• Journal of the Korean Chemical Society
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• v.54 no.2
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• pp.248-256
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• 2010

This study investigated the effects of the level of enrichment for analogies upon students' mapping, conceptual understanding, and the types of mapping errors in concept learning about Boyle's Law. Analogical reasoning ability test was administered and the score was used as a blocking variable. Three types (simple, enriched, and extended analogies) of learning materials according to the level of enrichment for analogies were studied by randomly assigned middle school students, and a conceptions test and a mapping test were administered immediately. The retention tests of both were administered four weeks later. Analyses of the results revealed that there was no main effect in the level of enrichment for analogies, but there was interaction effect with analogical reasoning ability in the post test on mapping. And the score of enriched analogy group was significantly higher than those of simple analogy group, but the score differences among three groups were not significant in the retention test on conceptual understanding. The frequency of the total mapping errors in the simple analogy group was the highest, and the frequencies of most types of mapping errors in the enriched and the extended analogy groups were less than those in the simple analogy group. There were also some differences in the frequencies of mapping errors with respect to the level of analogical reasoning ability. Therefore, these results will help science teachers plan and practice instructions using analogy.

• Korean Journal of Remote Sensing
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• v.15 no.3
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• pp.253-266
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• 1999

ADEOS(Advanced Earth Observing Satellite)/IMG(Interferometric Monitor for Greenhouse Gases) measurements - temperature, water vapor($H_2O$), ozone($O_3$) have been compared with the radio sonde and ozone sonde observations at Osan and Pohang stations for the 4 cases on 10 Jan.(a), 28 Jan.(b), 2 Apr.(c), and 19 Jun.(d) 1997 to detect the error ranges of the IMG data. It showed that the IMG data of the cases (b), (d) when the ADEOS passed over the central part of Korea were quite stable with the good agreement with the sonde observations, however, that of (a),(c) when the ADEOS passed over south- east coastal area were unstable with the larger differences from the sonde-observations. The RMSE and bias analyses of temperature for the stable cases (b),(d) showed that the differences between the IMG data and the sonde observations were about 1~4 K at the 700~300 hPa level and about 4~5 K or more at the higher level, and the IMG measurements tended to be larger than the sonde observations at the higher level above 200 hPa, while no typical bias was seen at the lower level. The RMSE and bias analysis for the version of level 2 5_6_4_4 of ozone showed that the RMSE of ozone were quite small, in general, except at the higher level above 50~60 hPa in the all 4 cases, however the bias was generally big with the positive value in the troposphere and the negative in the stratosphere. An example of vertical profile of trace gases such as $CO_2, N_2O, CH_4, HNO_3$, CO measured by IMG was also presented and it showed that the IMG data had large differences between the 5 different observation points.

• Journal of IKEEE
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• v.22 no.4
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• pp.1006-1011
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• 2018

This paper proposes a three level buck converter utilizing multi-bit flying capacitor voltage control. The conventional three-level buck converter can not control the flying capacitor voltage, so that the operation is unstable or the circuit for controlling the flying capacitor voltage can not be applied to the PWM mode. Also when the load current is increased, an error occurs in the inductor voltage. The proposed structure can control the flying capacitor voltage in PWM mode by using differential difference amplifier and common mode feedback circuit. In addition, this paper proposes a 3bit flying capacitor voltage control circuit to optimize the operation of the three level buck converter depending on the load current, and a triangular wave generation circuit using the schmitt trigger circuit. The proposed 3-level buck converter is designed in $0.18{\mu}m$ CMOS process and has an input voltage range of 2.7V~3.6V and an output voltage range of 0.7V~2.4V. The operating frequency is 2MHz, the load current range is 30mA to 500mA, and the output voltage ripple is measured up to 32.5mV. The measurement results show a maximum power conversion efficiency of 85% at a load current of 130 mA.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.5
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• pp.275-280
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• 2002

In order to control glucose concentration during fed-batch culture for antibiotic production, we applied so called “software sensor” which estimates unmeasured variable of interest from measured process variables using software. All data for analysis were collected from industrial scale cultures in a pharmaceutical company. First, we constructed an estimation model for glucose feed rate to keep glucose concentration at target value. In actual fed-batch culture, glucose concentration was kept at relatively high and measured once a day, and the glucose feed rate until the next measurement time was determined by an expert worker based on the actual consumption rate. Fuzzy neural network (FNN) was applied to construct the estimation model. From the simulation results using this model, the average error for glucose concentration was 0.88 g/L. The FNN model was also applied for a special culture to keep glucose concentration at low level. Selecting the optimal input variables, it was possible to simulate the culture with a low glucose concentration from the data sets of relatively high glucose concentration. Next, a simulation model to estimate time course of glucose concentration during one day was constructed using the on-line measurable process variables, since glucose concentration was only measured off-line once a day. Here, the recursive fuzzy neural network (RFNN) was applied for the simulation model. As the result of the simulation, average error of RFNN model was 0.91 g/L and this model was found to be useful to supervise the fed-batch culture.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.144-158
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• 2012

In this study, science teachers' and students' perceptions were searched on lectures and experiment of law of definite proportion in middle school science classes. For this study, the three teachers' lessons were observed and recorded, following interviews related to teachers' perceptions on the lessons and experiments. Also, We analyzed students' science scores, cognitive levels, science attitude, experimental reports, etc. According to the results, the three teachers had different focuses in the lectures. Chemistry teachers accentuated calculation of proportions and application rather than basic conceptions. But the students could not understand basic conceptions properly. The teachers spend long time to explain experimental procedures by assuming a low performance level of students in experimental classes. And the teachers had negative perceptions about error of results. The students could not understand the experiment results well, tried to manipulate data artificially, and had negative perceptions about error of results like the teachers. We suggested that these problems might be solved by changing teachers' perceptions on school science lectures and experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1923-1930
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• 2004

This paper presents digital microflow controllers(DMFC), where a fluidic digital-to-analog converter(DAC) is used to achieve high-linearity, fine-level flow control for applications to precision biomedical dosing systems. The fluidic DAC, composed of binary-weighted flow resistance, controls the flow-rate based on the ratio of the flow resistance to achieve high-precision flow-rate control. The binary-weighted flow resistance has been specified by a serial or a parallel connection of an identical flow resistor to improve the linearity of the flow-rate control, thereby making the flow-resistance ratio insensitive to the size uncertainty in flow resistors due to micromachining errors. We have designed and fabricated three different types of 4-digit DMFC: Prototype S and P are composed of the serial and the parallel combinations of an identical flow resistor, while Prototype V is based on the width-varied flow resistors. In the experimental study, we perform a static test for DMFC at the forward and backward flow conditions as well as a dynamic tests at pulsating flow conditions. The fabricated DMFC shows the nonlinearity of 5.0% and the flow-rate levels of 16(2$^{N}$) for the digital control of 4(N) valves. Among the 4-digit DMFC fabricated with micromachining errors, Prototypes S and P show 27.2% and 27.6% of the flow-rate deviation measured from Prototype V, respectively; thus verifying that Prototypes S and P are less sensitive to the micromachining error than Prototype V.V.

• Journal of Digital Contents Society
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• v.19 no.4
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• pp.789-799
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• 2018

This article presents machine learning based approach on Big data to analyzing time series data for anomaly detection in such industrial complex system. Long Short-Term Memory (LSTM) network have been demonstrated to be improved version of RNN and have become a useful aid for many tasks. This LSTM based model learn the higher level temporal features as well as temporal pattern, then such predictor is used to prediction stage to estimate future data. The prediction error is the difference between predicted output made by predictor and actual in-coming values. An error-distribution estimation model is built using a Gaussian distribution to calculate the anomaly in the score of the observation. In this manner, we move from the concept of a single anomaly to the idea of the collective anomaly. This work can assist the monitoring and management of Smart Factory in minimizing failure and improving manufacturing quality.

• Journal of the Korean Society of Safety
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• v.35 no.1
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• pp.97-106
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• 2020

The objective of this paper is to suggest a new quantification method for multi-unit probabilistic safety assessment (PSA) that removes the overestimation error caused by the existing delete-term approximation (DTA) based quantification method. So far, for the actual plant PSA model quantification, a fault tree with negates have been solved by the DTA method. It is well known that the DTA method induces overestimated core damage frequency (CDF) of nuclear power plant (NPP). If a PSA fault tree has negates and non-rare events, the overestimation in CDF drastically increases. Since multi-unit seismic PSA model has plant level negates and many non-rare events in the fault tree, it should be very carefully quantified in order to avoid CDF overestimation. Multi-unit PSA fault tree has normal gates and negates that represent each NPP status. The NPP status means core damage or non-core damage state of individual NPPs. The non-core damage state of a NPP is modeled in the fault tree by using a negate (a NOT gate). Authors reviewed and compared (1) quantification methods that generate exact or approximate Boolean solutions from a fault tree, (2) DTA method generating approximate Boolean solution by solving negates in a fault tree, and (3) probability calculation methods from the Boolean solutions generated by exact quantification methods or DTA method. Based on the review and comparison, a new intersection removal by probability (IRBP) method is suggested in this study for the multi-unit PSA. If the IRBP method is adopted, multi-unit PSA fault tree can be quantified without the overestimation error that is caused by the direct application of DTA method. That is, the extremely overestimated CDF can be avoided and accurate CDF can be calculated by using the IRBP method. The accuracy of the IRBP method was validated by simple multi-unit PSA models. The necessity of the IRBP method was demonstrated by the actual plant multi-unit seismic PSA models.

• Journal of Digital Convergence
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• v.14 no.10
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• pp.261-269
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• 2016

This paper aims to propose a novel technology of network convergence to provide ultra high speed internet services over CATV networks, by which a CMC(cable modem concentrator) and CM(cable modem) of 1Gbps level are designed. This technology not only lowers the production cost in comparison to the existing bonding technology with DOCSIS specification but also enables the adjustment of data speed based on the channel bandwidth. According to the experiments, when convolutional code rate with 128QAM is changed to 1/2, 2/3, 3/4 and 7/8, the data recorded the maximum transmission speed of up to 299 Mbps at the zero error rate. As the convolutional code rates with 256QAM is increased, it showed 334Mbps at the error rate of $10^{-5}$. Based on the findings of this paper, if we secure the channel bandwidth of 200MHz and adjust the modulation order of QAM and the convolution code rate depending on the channel status, we can get the transmission speed of more than 1Gbps, which is much more competitive in its function and price than the existing technology based on DOCSIS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.3
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• pp.192-199
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• 2018

This paper proposes an improved discrete Fourier transform spread single sideband(DFT-s-SSB) orthogonal frequency division multiplexing(OFDM) system that solves the problems of conventional DFT-s-SSB OFDM systems. Conventional DFT-s-SSB systems use pulse amplitude modulation(PAM) for applying SSB modulation. The higher the modulation level, the worse is the BER performance. Further, transmission is possible only through the lower sideband(LSB) spectrum. When transmitting using the LSB and upper sideband(USB) spectra simultaneously, interference occurs and spectrum recovery is not performed correctly. To solve this problem, the proposed system applies the 2/3 convolution coding to improve the bit error rate(BER) performance, adjusts the DFT size, and selects the USB spectrum to utilize the remaining spectrum resources. In addition, when using this system in an environment that supports multiuser or limited bandwidth, it uses only half of the spectrum; therefore, it can utilize the remaining spectrum resources and improve the spectral efficiency.